Vehicle camshaft connecting rods are utilized to connect a camshaft to a piston. Typically, a rod has an attachment portion at one end which is attached to the piston. The other end of the rod leads to two separable bolted portions which are positioned on the crankshaft and then bolted together.
It is desirable that the connection surfaces between the two bolted portions match as closely as possible. To achieve this goal, known systems use a connecting rod preform. The two bolted portions are initially formed integrally with a fracture plane formed between the bolted portions as a preform. This preform is placed on a connecting rod fracturing machine.
In known connecting rod fracturing machines, the preform is placed on a split mandrel, with the mandrel received in a central opening of the connecting rod. A ram is driven to force opposed mandrel portions away from each other, and crack the preform along the fracture plane. When the preform cracks along the fracture plane, the two bolted portions have opposed surfaces which should interfit very closely.
There is a good deal of effort made in the field of connecting rod fracturing machines to ensure that the fracture of the preform occurs as cleanly through the fracture plane as possible.
In one known system disclosed in U.S. Pat. No. 5,503,317, a hold down structure is forced by a wedge lock onto bolt shoulders on the top of the preform. The bottom of the preform sits on a fixed base. This structure locks the preform during fracturing. While this system is a great improvement upon the prior art, it would still be desirable to improve upon this known system.
In a disclosed embodiment of this invention, a machine for fracturing connecting rods has clamps which lock both bottom and top portions of the connecting rod preform. In a preferred embodiment, once the preform is mounted onto the mandrel, wedges are driven through angled grooves to force and lock the clamps onto the top and bottom portions of the preform. In a preferred embodiment, both the top and bottom clamps provide opposed hold down portions on each side of the preform that move as a single unit.
In the preferred embodiment, both top and bottom clamps are formed of two portions to allow adjustment. In a preferred embodiment the top clamp includes a rear portion which has the groove for being actuated by the wedge. A front portion of the top clamp includes the hold down elements. A small spacer is placed between the rear and forward portions, and the two portions are bolted to each other through the spacer. Thus, there is a small gap between the two portions. As the forward portion of the top clamp is brought into contact with the bolt shoulders of the preform, the small space allows the forward portion to rock slightly relative to the rear portion to adjust for any manufacturing tolerances between the two bolt shoulders. Thus, the top clamp is adjustable to accommodate the shape of the particular preform.
In a preferred embodiment, the bottom clamp includes forward and rear portions which are connected along an arc, such that the forward and rear portion can rock relative to each other along the arc. An arc-shaped interconnection finger is formed on both the rear and forward bottom clamp. The rear bottom clamp portion is formed with the angled groove, and the wedge moves through the groove to force the rear portion toward the preform shoulders. The rear portion drives the forward portion against the preform shoulders. The interfitting fingers of the rear and forward portions allow relative movement of the two portions along the arc-shaped interconnection to accommodate the shape of the individual preform. However, once the forward member is in contact with the preform, the wedge lock ensures that it is locked securely, and will not move during preform fracture.
In further features of this invention, two adjustable contact members provide the actual contact between the bottom clamp and the preform. The contact members have a cylindrical portion received in a hole in the forward portion. The portion of the contact member which contacts the preform is preferably polygonal, and can adjust to a straight surface on the preform. The contact member adjusts to accommodate the particular shape of the preform, and will turn within the cylindrical hole. The contact member and the arc-shaped interconnection ensure that the lower clamp does adjust to conform to the shape of the particular preform being fractured.